Combustion with extremely low pollutant content for lean premixing flames can be achieved if the reaction zone is spread spatially to a considerable degree if no rapid back mixing of exhaust gas with the fresh gas mixture is effected. This was achieved, inter alia, by experiments with perfect premixing and catalytic flame retention baffles as well as with flame retention baffles in the center of a premixed flow. NOx emission values of about 5 ppm (15% O2) at 1750.degree. K. (1477.degree. C.) flame temperature and at a pressure of about 14 bar can be achieved by such a configuration. However, these flame baffles have operational difficulties. On the one hand their cooling is very problematic. On the other hand the mechanical connection between the flame retention baffle and the burner is often responsible for hot zones of the flame retention baffles facilitate the formation of ignition centers. The ignition centers cause a burn-through of these flame retention baffles, which constitutes a potential risk for the downstream turbine. Several attempts have been made by means of clamping devices to prevent the flame retention baffles from becoming detached. But the play especially between clamping device and body of the flame retention baffle offers ideal conditions for forming wall boundary layers via which flashback of the flame into the interior of the premixing section is bound to occur.